Found: The First Metal-Plated Syringe in a Living Creature

Indian scientists confirm nature's first (partially) metal-plated syringe in a common parasitic wasp.

The wasp taps the rock-hard fruit with its antenna, listening for the telltale reverberation of its prey locked inside. When it hears the sound it's searching for, the hunter suddenly stops and stretches its abdomen into the air in a cartoonish fashion—unsheathing a thin, flexible syringe more than twice the size of the insect's body. As the wasp vibrates this tool, its serrated edges slice through the plant's skin, bending and twisting through the fruit. Finally, it finds the larvae of another insect, which the wasp injects with its own egg—dooming the other bug's larva to be eaten from the inside out.

This horrifying parasitic fig wasp is no new discovery—in fact, it's commonly found in many regions across India. But a research team at the Indian Institute of Science in Bangalore has just published the first scientific breakdown of the wasp's strange tool. As they report today in The Journal of Experimental Biology, the insect's strange ovipositor—its egg-laying syringe—is partially metal-plated with zinc. While similar metallic amalgams have been hypothesized to exist in the ovipositors of other wasp species, this is the first ever confirmed.

"There are many different challenges for this one tool," says Namrata Gundiah, a biomechanical engineer that led the research team. "It must be hard but flexible so that the female wasp can curve and bore it through the fig. And the wasp must be able to use it repeatedly and efficiently without it wearing down or fracturing."

The size of the syringe-like tool presents another challenge. While it is twice the size of the waps's body, "this is only about 1/5th of the diameter of a human hair," says Lakshminath Kundanati, a biomechanical engineer with the research team.

Such a thin tool should buckle under pressure, Kundanati says. But the researchers found that the wasp's tool is remarkable both in composition and shape. The syringe is metal-plated only at the end, which helps to form a sharp, rigid tip, Gundiah says, while the wire-like body of the syringe remains flexible. And when it pushes into the fruit, she says, the tip's serrated sides slide back and forth against each other like a pair of alternating stabbing swords, and several sharp rail-guides ensure the syringe stays its course.

While the syringe's partially metal makeup (7 percent at the tip) is strange, it's not entirely unexpected. "Insects will sometimes use metals for reinforcement when they need parts of their [exoskeleton] to be as hard as possible," says Gregory Sutton, an insect researcher at the University of Bristol who was not involved in the research. Sutton points to the mandibles of certain species of ants, such as the trap jaw ant, which can contain significant levels of magnesium and zinc.

And the finding isn't just a cool example of evolution. Gundiah and Kundanati say that the wasp's ovipositor could be a blueprint of a new design of micro-syringe for minimally invasive surgery. Sutton agrees: The wasp's tool is flexible, capable of repeated use without dulling, and, perhaps most importantly, made of easily sourced materials.

"This is not some high-cost, futuristic super-composite," Sutton says. "Nature is always trying to get the biggest bang for the cheapest buck. This made from just the 8 basic elements in life's toolbox."

Sutton, who was part of a team that discovered the first mechanical gear in nature, says what is also fascinating about this discovery is that it was found in a very common insect.

"You don't have to travel far off and go visit some obscure mountain in Tibet or some uncharted jungle outside Montevideo to find insects with these fascinating properties," he says. "We're barely started to scratch the surface of what lives in our own backyards."

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